A model for the localization of the acetylcholine receptors at the endplate has been proposed. Possible mechanisms underlying the localization are discussed, along with experiments which may clarify whether they are indeed valid. If the exposure to acetylcholine is prolonged, the endplate membrane loses sensitivity to ACh (densitization). One explanation for this is that the calcium that crosses the endplate membrane may, over times of seconds, close the ACh activated ionic channels from the inside. It is proposed to study this by altering the interval calcium levels. Chromaffin cells release granules from vesicles in the presence of ACh or barium, and this likely similar to the release of ACh at the nerve terminal. In chromaffin cells, the release is accompanied by the formation of microspikes 0.5microns long and up to 15microns long. The mechanism of formation of these structures is to be examined.